1. Field of the Invention
The present invention relates to container forming machines, and in particular to a new method and apparatus for forming containers of a type having rigid sidewalls that are uniquely attached to a central fiberboard or plastic wrap.
2. Description of the Prior Art
A wide variety of paperboard shipping and storage containers are known in the art. An equally wide variety of container forming machines are also known in the art. Among the more common uses of such containers are for the packing, shipment and storage of fresh fruit and vegetables, and for the storage and shipment of pre-packaged goods (e.g. cans of soup, bottles of beverages, jars of jelly, bags of rice, cartons of cereal, etc.). Such containers are typically made from paperboard materials such as, without limitation, single face corrugated, single wall (double-faced) corrugated, double wall corrugated, triple wall corrugated, container board, boxboard, linerboard, fiberboard and cardboard. There are many well known container styles that have been developed over the years, each being optimally suited for one or more particular products or industries.
Shipping and storage of fresh fruits such as table grapes pose particular problems because of the delicate nature of fruit, the cold temperatures in which the fruit is stored, and the need to pack, ship and store large quantities of fruit in reasonably sized containers.
Many paperboard containers have reinforced sides or end panels in order to improve stacking strength, such as that disclosed in U.S. Pat. No. 4,905,834. However, even with such reinforcements, these containers still suffer from significant stacking strength limitations because they are made of paperboard. The paperboard could easily become wet from such sources as rain, condensation in cold storage, ruptured fresh fruit, or the like, thereby losing stacking strength. Adding wax to such paperboard may improve resiliency, but also renders the paperboard container unrecyclable.
One known shipping container provides one or more fiberboard panels between two wooden end plates, the panels being nailed to the end plates. While the use of wood improves stacking strength of the container, such containers tend to slide against each other, particularly in taller stacks. In addition, the wooden end plates in the container may damage the fruit, the wood is expensive, and disengaging the nails and fiberboard from the wood panels is cumbersome, making such containers difficult to reuse or recycle. Replacing the wooden side panels of such containers with injection molded polypropylene can reduce the cost, but does not resolve the sliding problem, and exacerbates the recycling problem.
In response to these problems, a new container has been developed which is the subject of U.S. Pat. No. 5,497,939. This new container uses two specially designed plastic sidewalls (end panels) and a panel for attachment between them. Each plastic sidewall has stacking tabs on the top, corresponding receiving slots on the bottom, and a set of locking slots on the bottom and side edges thereof. The attachable panel includes a series of protruding lockable tabs along its sides, each tab having at least one opening therein. The panel is positioned between the two sidewalls such that the edges of the panel wrap around the sidewalls, the tabs on the panel engaging with the locking slots on the sidewalls to form a sturdy, stackable container. Forming such a container without the use of adhesives or nails allows the panel wrap to be cleanly and easily disengaged from the sidewalls, thereby allowing the wrap to be recycled and the sidewalls to be reused. Accordingly, a method and apparatus are needed to form the unique containers of U.S. Pat. No. 5,497,939.
In particular, such containers require an apparatus which is capable of firmly holding the plastic sidewalls in place, attaching the panel wrap to the sidewalls by engaging the tabs on the wrap with the locking slots on the bottom and side edges of the sidewalls, and preventing the central portion of the panel wrap from being bent or deformedxe2x80x94all without using adhesives or nails.
Virtually all paperboard machines use adhesives to bond the various pieces of the paperboard container together. Some machines fold a single paperboard blank into a container having a particular shape, such as that shown in U.S. Pat. No. 3,858,489; and others fold and eventually join together two or more paperboard pieces to form the container, such as that shown in U.S. Pat. No. 4,238,188.
U.S. Pat. No. 4,637,544 discloses a container box having two synthetic side walls connected by a folded sheet of cardboard. However, both side walls include U-shaped grooves recessed in the faces thereof for receiving the edges of the folded cardboard piece. A set of teeth found in the grooves are used to fasten the side walls to the folded cardboard piece. Thus, the cardboard piece must first be folded and placed in an exact position, then each of the side walls must be precisely inserted over the ends of the folded piece in order for the edges of the piece to fit into the grooves and engage the teeth. This patent does not disclose any apparatus for accomplishing this task. By contrast, the panel of the container formed by the present invention interlocks with locking slots on the exterior edge surfaces of the sidewalls, by engages a series of panel tabs with locking slots in the sidewalls.
The present invention provides a method and apparatus for forming containers of the type described which utilizes a mandrel movably mounted on a path between retracted and extended positions. The cycle for forming a container begins with full retraction of the mandrel. After being retracted, the mandrel moves forward to first receive the two synthetic sidewalls of the container to be formed, one on either side. The sidewalls are firmly compressed against the mandrel using pressure plates on either side. A rectangular fiberboard or plastic body panel or panel wrap is placed in the path of the mandrel in a vertical orientation.
The panel wrap includes a plurality of tabs along the edges of its two longer sides. These tabs correspond to locking slots on the surfaces of the bottom and side edges of the sidewalls. Each tab has an opening therein for receiving a corresponding button located in each slot on the sidewall. A series of plows and shoes are provided above and below the path of the mandrel on the other side of the wrap. As the mandrel moves forward, it pushes into the middle of the wrap. At the same time, the plows and shoes bend the upper and lower portions of the wrap into a more horizontal orientation, leaving the middle of the wrap in a vertical position. As the mandrel continues forward, the outside edges of the wrap come into contact with the exterior surface edges of the two sidewalls. As described more fully in the ""939 container patent, each of the sidewalls includes a plurality of locking slots or recesses with buttons therein on its outer edges for engagement with the tabs and openings of the panel wrap. In a typical embodiment, there are two (2) such recess-and-button areas on either end of each side panel, and three (3) such areas on the bottom of each panel.
As the wrap is pushed through the machine, a set of moveable upper and lower rockers press the panel wrap tabs on the horizontally oriented portion of the wrap into the locking slots on the ends of the sidewalls with sufficient pressure to not only force the tabs into the slots, but to also push the tabs onto the sidewall buttons such that the buttons extend through the openings in the body panel tabs. This pressure occurs as the container parts pass through the rockers. As a result, the tabs in the horizontally oriented (bent) portions of the wrap are locked to the upper and lower edges of the sidewalls.
Then, when the mandrel is fully extended, pressure is applied to the tabs on the vertically oriented middle section of the wrap (which will form the bottom of the container to be formed) in order to lock the remaining panel wrap tabs in this section to the corresponding slots and buttons on the bottom edges of the two sidewalls. Pressure is applied to these remaining tabs using a pair of hinge-mounted pressure plates fitted with unique biased brackets, each plate providing pressure to the tabs on one side of the wrap. The brackets push the tabs into the corresponding sidewall locking slots with sufficient force to also push the buttons through the holes in the tabs. The sidewalls are then released by the mandrel, the hinged end plates are opened, and the resulting container is removed from the machine. The mandrel is then fully retracted, and the machine begins another cycle. The result is a container constructed without the use of glue or nails that is very strong, and which is ready to be loaded, closed, stacked and shipped.
Other unique features of the machine include offset shoes or plows which provide unique engagement of the panel wrap both above and below the sidewall areas. These offset shoes prevent the open area of the panel wrap between the sidewalls from being bent or deformed as the tabs are locked to the sidewalls. Also unique is a brace on each side which holds the sidewall in place against the mandrel and securely aligns it as it passes between the pressure rockers. These braces prevent the sidewalls from slipping or shifting in order to assure that the panel wrap tabs line up with the locking slots in the sidewalls and to assure that the buttons in the sidewalls line up with the openings in the tabs. Another unique feature is the use of cables to transmit and/or impart motion from one or more centrally rotating cams out to the rockers and pressure plates of the machine.
It is therefore a primary object of the present invention to provide a method and apparatus for forming containers having two plastic sidewalls attached to a central plastic or fiberboard panel wrap without the use of adhesives or nails.
It is also an important object of the present invention to provide a method and apparatus for forming containers having two plastic sidewalls having a plurality of recesses and buttons on their peripheral edges that are engaged with a plurality of corresponding tabs with openings located along the edges of a plastic or fiberboard panel wrap.
It is another object of the present invention to provide a method and apparatus for forming containers of a type having two plastic sidewalls attached to a central panel wrap which causes a plurality of tabs with openings thereon located on the wrap to be engaged with a plurality of corresponding recesses and buttons located on the sidewalls for firm attachment of the panel to the sidewalls without the use of nails or glue.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which containers may be easily disassembled for recycling and/or reuse of the panel wrap and sidewalls.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which include tabs and slots at the tops and bottoms thereof, respectively, which allow for tall and stable stacking of such containers.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which containers are resistant to damage or collapse caused by moisture.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which utilizes offset shoes to prevent deformation of the panel as the tabs thereon are engaged with the sidewalls.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which utilizes a brace for securely holding the sidewalls in place as pressure is applied to attach the panel wrap tabs to the recesses and buttons thereon.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which utilizes unique cabling to impart motion from rotating cams to various distant operating parts of the machine.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which utilizes unique pressure rockers to attach the tabs and openings on the horizontally oriented panel sections to the corresponding locking slots and buttons on the sidewalls.
It is also an important object of the present invention to provide a method and apparatus for forming containers of the type described above which utilizes unique pressure plates and brackets to attach the tabs and openings on the vertically oriented panel wrap sections to the corresponding recesses and buttons on the sidewalls.
Other objects of the invention will be apparent from the detailed descriptions and the claims herein.